Mars had an oxygen-rich atmosphere around 4 billion years ago
13
Some asteroids have other asteroids orbiting them.
131
The temperature of the earth's interior increases by 1 degree every 60 feet down.
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In space, astronauts cannot cry properly, because there is no gravity, so the tears can't flow down their faces!
175
The earth rotates more slowly on its axis in March than in September.
145
The Sun and Moon appear to be the same size because the moon is 400 times smaller than the Sun, but 400 times closer to Earth.
13
A 100-pound person on Earth would weigh 38 pounds on Mars.
102
There are approximately 3,500 astronomers in the U.S. - but over 15,000 astrologers.
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